Editing Oligocene (section)

==Tectonics and paleogeography==
[[File:Mediterranean Rupelian.jpg|thumb|upright=1.2|[[Neotethys]] during the Oligocene (Rupelian, 33.9–28.4 mya)]]
During the Oligocene Epoch, the continents continued to [[continental drift|drift]] toward their present positions.{{sfn|Prothero|2005|pp=476–477}}<ref name=Torsvik>{{cite book |last1=Torsvik |first1=Trond H. |last2=Cocks |first2=L. Robin M. |title=Earth history and palaeogeography |date=2017 |publisher=Cambridge University Press |location=Cambridge, United Kingdom |isbn=9781107105324 |pages=241–245}}</ref>
[[Antarctica]] became more isolated as deep ocean channels were established between Antarctica and Australia and [[South America]]. Australia had been very slowly rifting away from West Antarctica since the Jurassic, but the exact timing of the establishment of ocean channels between the two continents remains uncertain. However, one estimate is that a deep channel was in place between the two continents by the end of the early Oligocene.{{sfn|Torsvik|Cocks|2017|pp=251–252}} The timing of the formation of the [[Drake Passage]] between South America and Antarctica is also uncertain, with estimates ranging from 49 to 17 mya (early Eocene to Miocene),<ref>{{cite journal |last1=Scher |first1=H. D. |last2=Martin |first2=E. E. |title=Timing and Climatic Consequences of the Opening of Drake Passage |journal=Science |date=21 April 2006 |volume=312 |issue=5772 |pages=428–430 |doi=10.1126/science.1120044|pmid=16627741 |bibcode=2006Sci...312..428S |s2cid=19604128 }}</ref> but oceanic circulation through the Drake Passage may also have been in place by the end of the early Oligocene.{{sfn|Prothero|2005|pp=474, 476}}{{sfn|Torsvik|Cocks|2017|pp=251–252}} This may have been interrupted by a temporary constriction of the Drake Passage from sometime in the middle to late Oligocene (29 to 22 mya) to the middle Miocene (15 mya).<ref>{{cite journal |last1=Lagabrielle |first1=Yves |last2=Goddéris |first2=Yves |last3=Donnadieu |first3=Yannick |last4=Malavieille |first4=Jacques |last5=Suarez |first5=Manuel |title=The tectonic history of Drake Passage and its possible impacts on global climate |journal=Earth and Planetary Science Letters |date=30 March 2009 |volume=279 |issue=3–4 |pages=197–211 |doi=10.1016/j.epsl.2008.12.037|bibcode=2009E&PSL.279..197L |url=https://hal.archives-ouvertes.fr/hal-00413525 }}</ref>

The reorganization of the oceanic tectonic plates of the northeastern Pacific, which had begun in the Paleocene, culminated with the arrival of the Murray and Mendocino Fracture Zones at the North American subduction zone in the Oligocene. This initiated strike-slip movement along the [[San Andreas Fault]] and [[extensional tectonics]] in the [[Basin and Range province]],{{sfn|Torsvik|Cocks|2017|p=245}} ended volcanism south of the Cascades, and produced clockwise rotation of many western North American terranes. The Rocky Mountains were at their peak. A new volcanic arc was established in western North America, far inland from the coast, reaching from central Mexico through the [[Mogollon-Datil volcanic field]] to the [[San Juan volcanic field]], then through Utah and Nevada to the ancestral Northern Cascades. Huge ash deposits from these volcanoes created the [[White River Group|White River]] and [[Arikaree Group]]s of the High Plains, with their excellent fossil beds.{{sfn|Prothero|2005|p=477}}

Between 31 and 26 mya, the [[Ethiopia-Yemen Continental Flood Basalts]] were emplaced by the East African [[large igneous province]], which also initiated rifting along the [[Red Sea]] and [[Gulf of Aden]].{{sfn|Torsvik|Cocks|2017|pp=241, 249}}

The [[Alps]] were rapidly rising in [[Europe]] as the [[African plate]] continued to push north into the [[Eurasian plate]], isolating the remnants of the [[Tethys Sea]].{{sfn|Prothero|2005|pp=476–477}}{{sfn|Torsvik|Cocks|2017|pp=241–245}} Sea levels were lower in the Oligocene than in the early Eocene, exposing large coastal plains in Europe and the Gulf Coast and Atlantic Coast of North America. The [[Obik Sea]], which had separated Europe from Asia, retreated early in the Oligocene, creating a persistent land connection between the continents.{{sfn|Prothero|2005|pp=476–477}} The [[Paratethys Sea]] stretched from what is now the [[Balkan Peninsula]] across [[Central Asia]] to the [[Tian Shan]] region of what is now [[Xinjiang]].<ref>{{cite journal |last1=Li |first1=Qian |last2=Li |first2=Long |last3=Zhang |first3=Yuanyuan |last4=Guo |first4=Zhaojie |date=20 April 2020 |title=Oligocene incursion of the Paratethys seawater to the Junggar Basin, NW China: insight from multiple isotopic analysis of carbonate |journal=[[Scientific Reports]] |volume=10 |issue=1 |page=6601 |doi=10.1038/s41598-020-63609-0 |pmid=32313139 |pmc=7170927 |bibcode=2020NatSR..10.6601L }}</ref> There appears to have been a land bridge in the early Oligocene between North America and Europe, since the [[Fauna (animals)|faunas]] of the two regions are very similar.<ref>{{cite book |last1=Denk |first1=Thomas |last2=Grímsson |first2=Friðgeir |last3=Zetter |first3=Reinhard |last4=Símonarson |first4=Leifur A. |title=Late Cainozoic Floras of Iceland |chapter=The Biogeographic History of Iceland – the North Atlantic Land Bridge Revisited |series=Topics in Geobiology |date=2011 |volume=35 |pages=647–668 |doi=10.1007/978-94-007-0372-8_12|isbn=978-94-007-0371-1 }}</ref> However, towards the end of the Oligocene, there was a brief marine incursion in Europe.<ref>{{cite journal |last1=Rousse |first1=Stephane |last2=Duringer |first2=Philippe |last3=Stapf |first3=Karl R. G. |title=An exceptional rocky shore preserved during Oligocene (Late Rupelian) transgression in the Upper Rhine Graben (Mainz Basin, Germany): OLIGOCENE ROCKY SHORE |journal=Geological Journal |date=July 2012 |volume=47 |issue=4 |pages=388–408 |doi=10.1002/gj.1349|s2cid=129895800 }}</ref><ref>{{cite journal |last1=Filek |first1=Thomas |last2=Hofmayer |first2=Felix |last3=Feichtinger |first3=Iris |last4=Berning |first4=Björn |last5=Pollerspöck |first5=Jürgen |last6=Zwicker |first6=Jennifer |last7=Smrzka |first7=Daniel |last8=Peckmann |first8=Jörn |last9=Kranner |first9=Matthias |last10=Mandic |first10=Oleg |last11=Reichenbacher |first11=Bettina |last12=Kroh |first12=Andreas |last13=Uchman |first13=Alfred |last14=Roetzel |first14=Reinhard |last15=Harzhauser |first15=Mathias |title=Environmental conditions during the late Oligocene transgression in the North Alpine Foreland Basin (Eferding Formation, Egerian) – A multidisciplinary approach |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |date=July 2021 |volume=580 |page=110527 |doi=10.1016/j.palaeo.2021.110527|bibcode=2021PPP...58010527F |doi-access=free }}</ref>

The rise of the Himalayas during the Oligocene remains poorly understood. One recent hypothesis is that a separate microcontinent collided with south Asia in the early Eocene, and India itself did not collide with south Asia until the end of the Oligocene.<ref>{{cite journal |last1=van Hinsbergen |first1=D. J. J. |last2=Lippert |first2=P. C. |last3=Dupont-Nivet |first3=G. |last4=McQuarrie |first4=N. |last5=Doubrovine |first5=P. V. |last6=Spakman |first6=W. |last7=Torsvik |first7=T. H. |title=Greater India Basin hypothesis and a two-stage Cenozoic collision between India and Asia |journal=Proceedings of the National Academy of Sciences |date=15 May 2012 |volume=109 |issue=20 |pages=7659–7664 |doi=10.1073/pnas.1117262109|pmid=22547792 |pmc=3356651 |bibcode=2012PNAS..109.7659V |doi-access=free }}</ref>{{sfn|Torsvik|Cocks|2017|p=241}} The [[Tibetan Plateau]] may have reached nearly its present elevation by the late Oligocene.<ref>{{cite journal |last1=DeCelles |first1=Peter G. |last2=Quade |first2=Jay |last3=Kapp |first3=Paul |last4=Fan |first4=Majie |last5=Dettman |first5=David L. |last6=Ding |first6=Lin |title=High and dry in central Tibet during the Late Oligocene |journal=Earth and Planetary Science Letters |date=January 2007 |volume=253 |issue=3–4 |pages=389–401 |doi=10.1016/j.epsl.2006.11.001|bibcode=2007E&PSL.253..389D }}</ref>

The Andes first became a major mountain chain in the Oligocene, as subduction became more direct into the coastline.{{sfn|Prothero|2005|p=477}}<ref name=Orme>{{Cite book
| last1  = Orme
| first1 = Antony R.
|editor-first1=Thomas T. 
|editor-last1=Veblen
|editor-first2=Kenneth R. 
|editor-last2=Young
|editor-first3=Anthony R.
|editor-last3=Orme
|editor-link1=Thomas T. Veblen
|chapter=The Tectonic Framework of South America
| title   = Physical Geography of South America 
| url  = https://archive.org/details/physicalgeograph00vebl
| url-access = limited
| pages   = [https://archive.org/details/physicalgeograph00vebl/page/n32 12]–17
| year    = 2007
|publisher=Oxford University Press
| isbn = 978-0-19-531341-3
}}</ref>